2-Amino-3-methylpyridinium, 2-amino-4-methylbenzothiazolium and 2-amino-5-chloropyridinium salts. Experimental and theoretical findings

• Published in: Journal of molecular structure Vol. 1222; p. 128914
• Main Authors: Hanif, Muhammad, Khan, Ezzat, Khalid, Muhammad, Tahir, Muhammad Nawaz, Morais, Sara Figueirêdo de Alcântara, Braga, Ataualpa Albert Carmo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.2020
• Subjects: 2-Amino-3-methylpyridine; 2-Amino-4-methylbenzothiazole; 3-Chlorobenzoic acid; Molecular salts; Salicylic acid; Secondary/noncovalent interactions; Molecular salts; Salicylic acid; 2-Amino-4-methylbenzothiazole; 3-Chlorobenzoic acid; 2-Amino-3-methylpyridine; Secondary/noncovalent interactions
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2020.128914

•Molecular salts of N-heterocyclic bases with salicylic and benzoic acid were obtained as crystals.•Molecular structure of three salts was determined by X-ray diffraction.•Non-covalent interactions in synthons have been discussed in details.•The AIM analysis of non-covalent interactions was carried out.•The O∙∙∙O, O∙∙∙S, Cl∙∙∙Cl, etc. collaborate to direct the supramolecular arrangements. Reaction between 2-amino-3-methylpyridine, 2-amino-4-methylbenzothiazole with salicylic acid, and 2-amino-5-chloropyridine with 3-chlorobenzoic acid were carried out and respective molecular salts 1–3 were obtained. During reactions, proton transfer from acid to endocyclic N of the base was observed. Structural elucidation of all compounds was carried out with the help of FT-IR and X-ray Diffraction for single crystals. The acid/base pairs in a molecular salt are held together with the help of H- and charge-assisted bonding and additional non-covalent bonding extend the supramolecular structure. All hydrogen bonds and secondary interactions have been discussed and a detailed comparison of experimental data with theoretical calculations through AIM, NBO and Wiberg bond index analysis has been made. The non-covalent character was mainly typified by positive values of Laplacian of electronic density. The theoretical studies demonstrate that other than classical H-bonds, the non-classical and secondary non-covalent interactions are very important to direct supramolecular structure of the respective molecular salt. The DFT calculations with solvent model SMD proved a good alternative to deduce the molecular salt formation when the 0>ΔpKa>3. Moreover, global reactivity descriptors (GRD) have been calculated utilizing the energies of FMOs. The calculated values for HOMO of compounds 1–3, -5.469, -5.642 and -6.435, respectively indicate that the compounds adopt the numerical order in terms of electron donation/Lewis basicity. The molecular salt formation is more feasible for heterosynthon 1 and least for 3. Reaction between 2-amino-3-methylpyridine, 2-amino-4-methylbenzothiazole with salicylic acid, and 2-amino-5-chloropyridine with 3-chlorobenzoic acid were carried out and respective heterosynthons 1–3 were isolated. Structural elucidation of all compounds was carried out with the help of FT-IR and X-ray Diffraction for single crystals. Experimental data was validated by DFT and noncovalent interactions are discussed in full detail. [Display omitted]